This invention relates to method and apparatus for forming web components for trusses. It pertains particularly to method and apparatus for forming a web component having a flat symmetrically bifurcated end at one extremity and a larger flattened end at the other extremity.
Composite, open ended trusses are known in the prior art for supporting various structures. They generally include upper and lower wooden chords separated by webbing. The webbing comprises a plurality of web components formed from steel tubing and having flattened web ends at each extremity. The web ends of adjacent web components are located side by side and are joined to one another and to the chords by means of coupling pins positioned through holes located in the web ends and in the chords. The chords either have slots for receiving the web ends or comprise separated paired elements.
In the application of these trusses the end or starter web component normally is tied at its upper end to the bearing wall supporting the truss by means such as a bearing clip. For this reason the starter web component carries a larger load than the other web components when the truss is loaded.
Since each panel point in the truss, other than the panel point at the upper end of the starter web component, ties two web ends and the associated chord together through a common coupling pin the web ends necessarily are offset from one another. Thus the pin loading is asymmetrical and when a load is applied a twisting moment is created, causing undue strain and wear, decreasing the load-carrying capability of the truss. The adverse effect of this asymmetrical loading is most pronounced at the lower end of the starter web component due to the fact that it carries a higher load, so that the capability of this panel point becomes a critical factor in determining the load capacity of the truss.
Accordingly, it has been the practice to make the end or starter web component heavier, utilizing a larger diameter coupling pin than is used in coupling the remaining web components.
To prevent the occurrence of the foregoing problem inherent in the starter web component of the prior art trusses, it also has been proposed to join a second web end to the lower portion of the web component alongside and separated from the existing web end in a bifurcated arrangement designed to create symmetrical coupling pin loading. However, under present practice this additional web end must be joined to the web component, by such means as welding, which is a time consuming and costly separate operation. In addition, the second web end necessarily is offset from the existing web end which is located on the longitudinal centerline of the web component. Therefore, the additional web end must be located to one side or the other of the longitudinal centerline of the web component creating a web component which will cause asymmetrical loading when installed in a truss.
Also, as noted one end of the starter web component is tied to the bearing wall which supports the truss. This is accomplished by means of a bearing clip. The ends of the prior art web components are short since they must withstand bending when coupled with another web component at a panel point. Therefore, when they are installed in the bearing clip, there is not sufficient flattened area on the web end to couple them properly without interference between the clip and the web component.
It is therefore the general purpose of the present invention to provide method and apparatus for forming a truss web component having a symmetrically bifurcated web end.
It is a further purpose of the present invention to provide a method and apparatus which also forms a comparatively larger flattened web end on the opposite end of the web component giving increased web end area facilitating tying the web component to the bearing wall with a bearing clip.
It is a further purpose of the present invention to provide method and apparatus for forming such a web component having web ends which will not infringe upon the adjoining surfaces of the truss chord or the supporting foundation.
It is a further purpose of the present invention to provide accurate, quick and safe apparatus for forming such a web component.
It is a further purpose of the present invention to provide an apparatus for forming such web components of different sizes and thicknesses.